Big Eye (ビッグアイ,Biggu Ai?) is a one-eyed surveillance robot with high defense that tries to crush its enemies. In the first Mega Man game, a single Big Eye appears in the stages of Cut Man (red), Guts Man (blue), Ice Man and Elec Man (red), and three metallic Big Eyes appear in the beginning of the final stage. They also appear in the first part of the Wily Tower in Mega Man: The Wily Wars. In Mega Man Powered Up, the opening stage boss is a larger Big Eye called Proto Eye that attacks with laser orbs and stomps.

Big Eyes are vulnerable on all parts of their body in the first game, while in Mega Man Powered Up their only weak spot is the eye, which closes when at rest. In Mega Man: Dr. Wily's Revenge, Big Eyes can only be damaged while they are jumping and appear in the stages of Cut Man, Ice Man, Elec Man and both Wily stages (Wily Castle and Wily Station respectively). They are weak against Super Arm and Thunder Beam. Although Big Eyes aren't damaged by Ice Slasher, they will be frozen, making fighting or passing by them significantly easier. It is best to freeze them at the peak of their high jump so Mega Man can walk underneath it safely.

Proto Eye (プロトアイ,Puroto Ai?) is the boss from the opening stage of Mega Man Powered Up. It is a larger, grey-colored version of a normal Big Eye that Dr. Wily sends after the player to cover his escape.

Proto Eye can attack with laser orbs, and how many it shoots depends on the game's difficulty setting. The Proto Eye is actually less dangerous than a regular Big Eye, since it deals less damage, is vulnerable on all parts of its body, and makes slower, wider jumps all at the same height, although this is understandable since it is merely an introductory boss for beginners to learn the basics on.